Devices, systems, and methods for real-time monitoring of electrophysical effects during tissue treatment

ABSTRACT

Provided herein are devices, systems, and methods for monitoring lesion or treated area in a tissue during focal ablation or cell membrane disruption therapy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 15/536,333, filed Jun. 15, 2017, which '333 Application is aNational Stage application under 35 U.S.C. § 371 of InternationalApplication No. PCT/US2015/065792, filed Dec. 15, 2015, whichinternational application claims the benefit of U.S. ProvisionalApplication Ser. No. 62/091,703 filed on Dec. 15, 2014 having the title“Real-Time Monitoring of Electrophysical Effects During Tissue FocalAblation”, each of which are herein incorporated by reference in theirentireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant numberIIP-1026421 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

BACKGROUND

Focal ablation and other cell membrane disruption therapies and moleculedelivery mechanisms are used in many clinical and research applications.As such, monitoring techniques for lesion/treatment area are desirable.As such, there exists a need for improved monitoring techniques for use,inter alia, focal ablation and other cell membrane disruption therapies.

SUMMARY

Provided herein are embodiments of an electrical conductivity sensorhaving an impedance sensor, where the impedance sensor can be configuredto measure a low-frequency and a high-frequency impedance and asubstrate, where the impedance sensor is coupled to the substrate. Thesubstrate can be flexible. In embodiments, the impedance sensor cancontain two or more electrical conductors. The electrical conductors canbe in a bipolar configuration. The electrical conductors can be in atetrapolar configuration. In embodiments, the electrical conductivitysensor can have two impedance sensors that can be coupled to thesubstrate such that they are orthogonal to each other.

In embodiments, the electrical conductivity sensor can have more thanone impedance sensor. In some embodiments, the impedance sensors can beconfigured in an array. In embodiments having more than one impedancesensor, the electrical conductivity sensor can further contain a commonground, where each impedance sensor is coupled to the common ground. Inembodiments having more than one impedance sensor, the electricalconductivity sensor can further contain a common counter electrode,wherein the common counter electrode can be coupled to the substrate.

In embodiments, the impedance sensor(s) can have interdigitatedelectrodes. In embodiments, the impedance sensor(s) can further containa receptor molecule configured to specifically bind a target molecule,wherein the receptor molecule is coupled to the sensor(s).

In embodiments, the electrical conductivity sensor can contain one ormore sensors configured to detect a tissue characteristic selected fromthe group of: pH, temperature, a chemical concentration, a nucleic acidconcentration, a gas amount, or combinations thereof.

Also provided herein are embodiments of an electrical conductivity probehaving an elongated member and an electrical conductivity sensor asdescribed herein where the electrical conductivity sensor can be coupledto the elongated member. In embodiments, the electrical conductivitysensor can be removably coupled to the elongated member.

Also provided herein are embodiments of a system having an electricalconductivity probe as described herein, a treatment probe configured todeliver an energy to a tissue, where the energy can be sufficient todisrupt a cell membrane, an impedance analyzer, where the impedanceanalyzer can be coupled to the electrical conductivity probe, a lowvoltage power supply, where the low voltage power supply can be coupledto the electrical conductivity probe and can be configured to deliver alow voltage energy to the electrical conductivity probe, a waveformgenerator, where the waveform generator can be coupled to the lowvoltage power supply, a gate driver, where the gate driver can becoupled to the waveform generator and the low voltage power supply, ahigh voltage switch, where the high voltage switch can be coupled to thetreatment probe and the impedance analyzer; and a high voltage powersupply, where the high voltage power supply can be coupled to the highvoltage switch.

In embodiments, the system can further contain a computer. The computercan be coupled to the impedance analyzer and the computer can containprocessing logic that can be configured to determine the position oflesion or treated area front within a tissue undergoing focalablation/cell membrane disruption therapy. The processing logic can befurther configured to generate a signal to a user when the position oflesion or treated area front has reached a predetermined position withinthe tissue. The processing logic can be configured to automaticallymanipulate the system to adjust or stop treatment of a tissue by thetreatment probe when the position of lesion or treated area front hasreached a predetermined position within the tissue.

In embodiments, the treatment probe and the electrical conductivityprobe can be the same probe. In embodiments, the treatment probe and theelectrical conductivity probe are separate probes. The treatment probecan be coupled to a grounding pad located elsewhere relative to thetreatment probe in or on the body of a subject being treated.

Also provided herein are embodiments of a method of monitoring thelesion or treated area front or size during focal ablation or cellmembrane disruption therapy, the method have the steps of inserting anelectrical conductivity probe as described herein into a tissue,inserting a treatment probe into the tissue, applying a treatment to thetissue, wherein the treatment comprises applying an energy to the tissuevia the treatment probe, and measuring a characteristic of the tissuecontinuously during treatment, determining if there is a change in thetissue characteristic. The characteristic can be impedance. In someembodiments, the step of measuring can include measuring bothlow-frequency impedance and high-frequency impedance and furthercomprising the step of stopping or adjusting treatment whenlow-frequency impedance is equal to high-frequency impedance. Inembodiments, the characteristic can be pH, temperature, a gasconcentration, a chemical concentration, a nucleic acid concentration,or a combination thereof. In some embodiments, the method can containthe step of stopping or adjusting a treatment when a change in thetissue characteristic is detected. In embodiments, the method cancontain the step of alerting a user when a change in the tissuecharacteristic is detected.

In some embodiments, where the electrical conductivity probe includes animpedance sensor array, the method can include the step of determiningthe location of the lesion or treated area front or size by comparingimpedance data between two or more impedance sensors of the impedancesensor array. In embodiments, the method can include the step ofcomparing the lesion or treated area front or size to a threshold valueand stopping treatment when lesion or treated area front or size isgreater than or equal to the threshold value. In embodiments, the methodcan include the step of comparing the lesion or treated area front orsize to a threshold value and alerting a user when lesion or treatedarea front or size is greater than or equal to the threshold value.

The method can include the steps of comparing measured changes inimpedance to a solution for the electric field distribution during focalablation or cell membrane disruption and determining the 2D/3D lesion ortreated area geometry of the lesion or treated area volume. Inembodiments, the method can include the step of overlaying the 2D/3Dlesion or treated area geometry on one or more medical images of asubject to generate an image overlay. The method can include the step ofvisualizing lesion or treatment area front migration or lesion ortreatment area growth from the image overlay.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be readily appreciatedupon review of the detailed description of its various embodiments,described below, when taken in conjunction with the accompanyingdrawings.

FIG. 1 shows embodiments of an electrical conductivity sensor.

FIG. 2 shows embodiments of an electrical conductivity sensor.

FIG. 3 shows embodiments of an electrical conductivity sensor.

FIG. 4 shows embodiments of an electrical conductivity sensor.

FIG. 5 shows embodiments of an electrical conductivity sensor.

FIG. 6 shows embodiments of an electrical conductivity sensor.

FIG. 7 shows embodiments of an electrical conductivity sensor.

FIG. 8 shows embodiments of an electrical conductivity sensor.

FIG. 9 shows embodiments of an electrical conductivity probe.

FIG. 10 shows embodiments of an electrical conductivity probe.

FIG. 11 shows embodiments of an electrical conductivity probe.

FIG. 12 shows embodiments of an electrical conductivity probe.

FIG. 13 shows embodiments of an electrical conductivity probe.

FIG. 14 shows embodiments of a system configured to monitorlesion/treated area formation in real-time.

FIG. 15 shows embodiments of a system configured to monitorlesion/treated area formation in real-time.

FIGS. 16A-16B show embodiments of operation of an electricalconductivity probe during treatment to monitor lesion/treated areaformation in real-time.

FIGS. 17A-17C show embodiments of operation of an electricalconductivity probe during treatment to monitor lesion/treated areaformation in real-time.

FIG. 18 shows an image of an embodiment of an electrical conductivitysensor.

FIG. 19 shows an image of an embodiment of an electrical conductivitysensor.

FIG. 20 shows an image of an embodiment of an electrical conductivitysensor.

FIG. 21 shows an image of an embodiment of an electrical conductivityprobe.

FIGS. 22A-22J shows steps in a process for manufacturing an electricalconductivity sensor.

FIGS. 23A-23B show a three dimensional finite element model to simulateIRE treatment of liver tissue with two needle electrodes.

FIGS. 24A-24B show the simulated electrical conductivity in the tissueresulted from IRE (FIG. 24A) and simulated extrapolation of pointspecific measurements in three dimensions to determine thespatial-temporal conductivity map and electric field distribution (FIG.24B).

FIGS. 25A and 25B show images of a probe FIG. 25A and placement within asample of porcine liver. The dashed circle in FIG. 2B indicates thetreated area. The black dots indicate location of the sensors of theprobe within the tissue.

FIG. 26 shows a graph demonstrating tissue resistance (ohms) afterdelivery of a series of high-frequency irreversible electroporation(HFIRE) pulses to the porcine liver of FIG. 25B as measured by the probeof FIG. 25A.

FIG. 27 shows a graph demonstrating % change in tissue resistancebetween varying sensors after delivery of a series of high-frequencyirreversible electroporation (HFIRE) pulses to the porcine liver of FIG.25B as measured by the probe of FIG. 25A.

FIGS. 28A-28D show images of a 3D isometric view of the probe ontoortho-planes from stacked CT images of patient anatomy.

FIGS. 29A-29C show graphs demonstrating finite element modeling (FEM) ofelectric field magnitude along the length of the probe in a potatomodel, where N=10 (FIG. 29A), N=30 (FIG. 29B), and N=100 (FIG. 29C).

FIGS. 30A-30C show graphs demonstrating experimental results ofconductivity change as measured by different sensor pairs along thelength of the probe in a potato model, where N=10 (FIG. 30A), N=30 (FIG.30B), and N=100 (FIG. 30C).

FIGS. 31A-31C show photos demonstrating experimental ablations afterdelivering a series of IRE pulses to a potato model where N=10 (FIG.31A), N=30 (FIG. 31B), and N=100 (FIG. 31C).

FIG. 32 shows embodiments of installation of a sensor array on a probeand the electrical connections to the sensor.

FIGS. 33A-33B shows the electrical impedance spectrum of the porcineliver (FIG. 33A) along with the equivalent circuit model of the tissue(FIG. 33B).

FIG. 34 shows an embodiment of a system where a monopolar electrode anda grounding pad are used to deliver the high voltage pulses.

FIG. 35 shows another embodiment of a system where a monopolar electrodeand a grounding pad are used to deliver the high voltage pulses.

DETAILED DESCRIPTION

Before the present disclosure is described in greater detail, it is tobe understood that this disclosure is not limited to particularembodiments described, and as such may, of course, vary. It is also tobe understood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the disclosure. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges and are also encompassed within the disclosure, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the disclosure.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present disclosure, the preferredmethods and materials are now described.

All publications and patents cited in this specification are hereinincorporated by reference as if each individual publication or patentwere specifically and individually indicated to be incorporated byreference and are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that the present disclosure is not entitled to antedate suchpublication by virtue of prior disclosure. Further, the dates ofpublication provided could be different from the actual publicationdates that may need to be independently confirmed.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentdisclosure. Any recited method can be carried out in the order of eventsrecited or in any other order that is logically possible.

Embodiments of the present disclosure will employ, unless otherwiseindicated, techniques of mechanical engineering, electrical engineering,physiology, medical science, veterinary science, bioengineering,biomechanical engineering, physics, and the like, which are within theskill of the art. Such techniques are explained fully in the literature.

Definitions

As used herein, “about,” “approximately,” and the like, when used inconnection with a numerical variable, generally refers to the value ofthe variable and to all values of the variable that are within theexperimental error (e.g., within the 95% confidence interval for themean) or within .+−0.10% of the indicated value, whichever is greater.

As used herein, “control” is an alternative subject or sample used in anexperiment for comparison purposes and included to minimize ordistinguish the effect of variables other than an independent variable.A “control” can be a positive control, a negative control, or an assayor reaction control (an internal control to an assay or reactionincluded to confirm that the assay was functional). In some instances,the positive or negative control can also be the assay or reactioncontrol.

As used interchangeably herein, “subject,” “individual,” or “patient,”refers to a vertebrate, preferably a mammal, more preferably a human.Mammals include, but are not limited to, murines, simians, humans, farmanimals, sport animals, and pets. The term “pet” includes a dog, cat,guinea pig, mouse, rat, rabbit, ferret, and the like. The term farmanimal includes a horse, sheep, goat, chicken, pig, cow, donkey, llama,alpaca, turkey, and the like.

As used herein, “biocompatible” or “biocompatibility” refers to theability of a material to be used by a patient without eliciting anadverse or otherwise inappropriate host response in the patient to thematerial or an active derivative thereof, such as a metabolite, ascompared to the host response in a normal or control patient.

As used herein, “therapeutic” can refer to curing and/or treating asymptom of a disease or condition.

The term “treating”, as used herein, can include inhibiting and/orresolving the disease, disorder or condition, e.g., impeding itsprogress; and relieving the disease, disorder, or condition, e.g.,causing regression of the disease, disorder and/or condition. Treatingthe disease, disorder, or condition can include ameliorating at leastone symptom of the particular disease, disorder, or condition, even ifthe underlying pathophysiology is not affected, such as treating thepain of a subject by administration of an analgesic agent even thoughsuch agent does not treat the cause of the pain.

The term “preventing”, as used herein includes preventing a disease,disorder or condition from occurring in a subject, which can bepredisposed to the disease, disorder and/or condition but has not yetbeen diagnosed as having it. As used herein, “preventative” can refer tohindering or stopping a disease or condition before it occurs or whilethe disease or condition is still in the sub-clinical phase.

The term “target molecule” can refer to any specific desired moleculeincluding, but not limited to, a nucleic acid, oligonucleotide,polynucleotide, peptide, polypeptide, chemical compound, or othermolecule that can specifically bind to a receptor molecule. Typically,the target molecule refers to a molecule that can be located in a sampleor tissue whose presence and/or amount can be determined by detectingits binding to known receptor molecule.

The term “receptor molecule” can refer to a molecule that canspecifically bind to a target molecule. A receptor molecule can be anucleic acid, oligonucleotide, polynucleotide, peptide, polypeptide,chemical compound, or other molecule. Receptor molecules can be, forexample, antibodies or fragments thereof or aptamers. The receptormolecule can be bound, fixed, or otherwise attached to a surface,sometimes in known location (e.g. as in an array), and can be exposed toa sample such that if a target molecule is present, the target moleculecan interact and specifically bind with the receptor molecule. Thespecific binding can, in some cases, trigger a signal that can providequantitative and/or qualitative information regarding the targetmolecule.

As used herein, “specific binding,” “specifically bound,” and the like,refer to binding that occurs between such paired species asnucleotide/nucleotide, enzyme/substrate, receptor/agonist,antibody/antigen, and lectin/carbohydrate that can be mediated bycovalent or non-covalent interactions or a combination of covalent andnon-covalent interactions. When the interaction of the two speciesproduces a non-covalently bound complex, the binding which occurs istypically electrostatic, hydrogen-bonding, or the result of lipophilicinteractions. Accordingly, “specific binding” occurs between a pairedspecies where there is interaction between the two which produces abound complex having the characteristics of an antibody/antigen orenzyme/substrate interaction. In particular, the specific binding ischaracterized by the binding of one member of a pair to a particularspecies and to no other species within the family of compounds to whichthe corresponding member of the binding member belongs. Thus, forexample, an antibody preferably binds to a single epitope and to noother epitope within the family of proteins.

As used herein, “aptamer” refers to single-stranded DNA or RNA moleculesthat can bind to pre-selected targets including proteins with highaffinity and specificity. Their specificity and characteristics are notdirectly determined by their primary sequence, but instead by theirtertiary structure.

Discussion

Focal cell ablation and focal cell membrane disruption techniques can beused to selectively destroy undesired tissue, deliver drugs to cells andtissues, and deliver nucleic acids to cells. Focal ablation and membranedisruption techniques can be thermally or non-thermally based. Thermallybased techniques use heat to ablate cells or disrupt cell membranes andinclude, but are not limited to, radiofrequency (RF) ablation, laserablation, cryo-ablation, and ultrasound. Other thermal focalablation/membrane disruption techniques will be appreciated by those ofordinary skill in the art. Non-thermal techniques can rely on thegeneration or application of an electric field to cells to disrupt(reversibly or irreversibly) the cell membrane, which increases thepermeability or kills the cells. Non-thermal focal ablation/membranedisruption techniques include, but are not limited to electroporation.Other Non-thermal focal ablation/membrane disruption techniques will beappreciated by those of ordinary skill in the art. During thesetechniques, it is difficult to determine the extent of treatment withina tissue being treated. As such, current procedures relying on focalablation and membrane disruption techniques are imprecise, which canresult in undesirable side effects, destruction of, orgene/transcript/protein modification in normal or otherwise healthycells.

Membrane permeability changes induced by focal ablation/cell membranedisruption techniques at the cell level can translate into changes inimpedance at the tissue level. Known devices and methods of monitoringtissue impedance, such as during electroporation, have severaldrawbacks. Primarily, they rely on bulk tissue properties as opposed tomeasurements at well-defined points within the tissue being treated.Bulk changes can be useful in describing how the dielectric propertiesof the tissue change as a whole during treatment. However, there is nospecificity in terms of the location where treatment is occurring. Inknown devices and methods, this information is usually inferred fromcorrelations with predications of the electric field distribution in thetissue. In other words, the treatment zone is defined as the area abovea pre-determined threshold that is based on the inferred correlationsand predications. The bulk measurements can be made either through thetreatment electrodes or with a separate set of electrodes, where theelectrodes located in proximity to each other.

As an alternative, electrical impedance tomography (EIT) can be used tomap the tissue dielectric potential throughout the entire treatmentregion based on solutions to a nonlinear inverse that accounts forsurface electrical measurements. However, this imaging technique iscomplicated by the required placement of an electrode array around theperiphery of the target tissue. Placement of the electrode array can bedifficult to implement clinically because some tumors and other targettissues do not accommodate the placement of such an array due togeometrical/anatomical constraints or the presence of highly insulatinganatomical structures such as the skull or skin. Further, EIT suffersfrom the limitations associated with the resolution of reconstructedimages, which relies heavily on the accurate placement and number ofexternal electrodes. Moreover, none of the existing technologies andmethods can achieve active, real-time monitoring of the lesion ortreated area front during focal ablation and cell membrane disruptionprocedures.

With these shortcomings in mind, described herein are devices andsystems that can be configured to monitor a lesion or treated area frontin real-time during focal ablation/membrane disruption therapy. Thedevices and systems can be configured with a sensor array to detect alesion or treated area front. The devices and systems provided hereincan be used to actively monitor focal ablation/cell membrane disruptiontherapy in real-time and thus can allow a practitioner to control,adjust, and/or discontinue treatment in response to front migration tominimize treatment side effects.

Also described herein are methods of monitoring a lesion or treated areafront in real-time in tissue during focal ablation/membrane disruption.The methods can include alerting a user when the front has reached adesired location. The methods can utilize both low- and high-frequencyelectrical impedance measurements to determine if the tissue areasurrounding a sensor has been ablated or treated. The devices, systemsand methods described herein can provide for focal ablation/membranedisruption techniques and therapies with improved specificity thancurrent techniques and devices. Other devices, systems, methods,features, and advantages of the present disclosure will be or becomeapparent to one having ordinary skill in the art upon examination of thefollowing drawings, detailed description, and examples. It is intendedthat all such additional compositions, compounds, methods, features, andadvantages be included within this description, and be within the scopeof the present disclosure.

Systems and Devices for Real-Time Impedance Monitoring

During focal ablation or cell membrane disruption procedures, as theprocedure continues the treated area or lesion expands out from thetreatment source. A feature common to these types of therapies is achange in the membrane permeability of the cell membranes that have beenstimulated during focal ablation or cell membrane disruption. Focalablation and other membrane disruption techniques can result in a changein impedance in due to a change in the permeability of the cells thathave been sufficiently stimulated during focal ablation or cell membranedisruption.

As the lesion or treated area forms as treatment continues, anincreasing number of cells in the tissue surrounding the treatmentsource undergo a membrane disruption and thus a change in the impedanceof the cells in that area. As the lesion/treated area grows, a front canbe formed that forms a boundary between treated and untreated cells. Thetreated cells and the untreated cells can have different impedances orother characteristics (e.g. pH and temperature). By measuring theimpedance or other characteristic between two or more points in thetissue during treatment, it can be possible to determine if the frontlies between those two points. The position of the lesion/treated areafront within a tissue being treated can also be made by measuringimpedance or other tissue characteristic at a single point and comparingthat to a base line or prior measurement from that point.

Provided herein are systems and devices that can be configured to detectand determine the location of a lesion/treated area front in real-timeduring a focal ablation or cell membrane disruption therapy. The systemsand devices can also be configured to generate 3D images and models fromlesion/treated area front measurements that can provide the volume of alesion/treated area. The systems and devices can be configured toprovide automatic control of a treatment in response to detection of themigration of the lesion/treated area front. The systems and devices canbe configured to provide a signal to a user in response to detection ofthe migration of the lesion/treated area front.

Biological tissue is a combination of extracellular space, cellularmembranes, and subcellular structures, each of which contains organicmolecules and ions in different structural arrangements. This can resultin a broad spectrum of dielectric properties across multiplefrequencies. In other words, the dielectric properties of tissue arefrequency dependent. From around 0.1 Hz to 10 MHz, there exist two maindispersive regions: (1) the α, or low frequency, dispersion region and(2) the β, or high frequency, region. The α region ranges from about 0.1Hz to about 10 Hz and the β region ranges from about 0.1 MHz to about 10MHz. The α region is due to counter ion polarization effects along cellmembranes. The β region is due to the Maxwell-Wagner effects. Thisdescribes the charging and relaxation effects along cell membranes,which act as barriers to the movement of ions.

Above the β dispersion, cell membranes have negligible impedance andcurrent can pass freely through the cell membrane. This is similar towhat happens during, for example, electroporation, when pore formationreduces the membrane impedance and permits current to enter the cell. Asa result, low frequency (α region) electrical measurements at a locationin a tissue before and after focal ablation or cell membrane disruptioncan be compared to determine if the focal ablation or cell membranedisruption has reached its endpoint at that position in the tissue. Atthe endpoint, the low frequency (α region) impedance is about equal tothe high-frequency (β region) impedance, which is due to the focalablation or cell membrane disruption in that region of the tissue.Stated differently, in a formed lesion or treated area, the lowfrequency (α region) impedance is about equal to the high-frequency (Rregion) impedance. Thus, comparison of the low frequency (α region)impedance and the high-frequency (β region) impedance can be used todetermine lesion formation in that area of tissue due to focalablation/cell membrane disruption treatment.

In some embodiments, the systems and devices can be configured to detecta focal ablation or cell membrane disruption in treatment area bysimultaneously measuring both a region and β region impedance in atissue. The systems and devices described herein can be configured tomonitor, in real-time, the size of a treated area during a focalablation or cell membrane disruption procedure. The devices and systemscan contain an electrical conductivity sensor, which can contain animpedance sensor or impedance sensor array. The electrical conductivitysensor can be configured to measure both low-frequency (a region)impedance and high-frequency (β region) impedance. The electricalconductivity sensor can be integrated with or operatively coupled to anelectrical conductivity probe and/or be integrated with or operativelycoupled to a treatment probe.

Electrical Conductivity Sensors With a general description in mind,attention is directed to FIGS. 1-8, which show embodiments of electricalconductivity sensors that can be configured to measure tissue impedance,a change in tissue impedance between points in a tissue, migration of alesion/treated area front, and/or both low-frequency (α region)impedance and high-frequency (β region) impedance.

Discussion begins with FIG. 1, which shows one embodiment of anelectrical conductivity sensor 100 that can be configured to measure achange in tissue impedance between points in a of tissue, and/or bothlow-frequency (α region) impedance and high-frequency (β region)impedance. The electrical conductivity sensor 100 can have an impedancesensor 110 at least two electrical conductors 120 a,b (collectively110). In some embodiments, the impedance sensor 110 can have an evennumber of electrical conductors 120. In some embodiments the impedancesensor 110 can have 2, 3, 4, 5, 6, 7, 8, 9, 10 or more electricalconductors 120. In some embodiments, the impedance sensor 110 can beconfigured to measure impedance using a bipolar configuration ofelectrodes 120 (see e.g. FIG. 1). In other embodiments, the impedancesensor 110 can be configured to measure impedance using a tetrapolarconfiguration (see e.g. FIG. 3). It will be appreciated that the sensorelectrodes, in any given configuration, can be separate from any sourceand sink electrodes that can be used for delivering the focalablation/cell membrane disruption therapy.

The electrical conductors 120 can be coupled to bonding pads 140 a,b(collectively 140). In some embodiments, each electrical conductor 120is coupled to an individual bonding pad 140. The electrical conductors120 can be coupled to the bonding pad(s) 140 via electrical leads 150a,b (collectively 150). The electrical conductor 120, the bonding pad(s)140, and the lead(s) 150 can be coupled to a substrate 160. In someembodiments, the electrical conductors 120 can be coupled to animpedance sensor substrate 130. The impedance sensor substrate 130 canbe coupled to the substrate 160. In some embodiments, the electricalconductors 120 can be attached directly to the substrate 160. Theelectrical conductivity sensor 100 can be configured such that at leasta portion of one or more of the electrodes is exposed to the tissue whenin use.

The electrical conductivity sensor 100 can have a length (l), a width(w), and a thickness. The length can range from about 1 mm to 1000 mm ormore. The width can range from about 0.1 mm to about 50 mm or more. Thethickness can range from about 0.1 micron to about 1000 microns or more.

As shown in FIG. 2, the electrical conductivity sensor 100 can beflexible. The substrate 160 and the optional impedance sensor substrate130 can be made out of any suitable material. The material can bebiocompatible. Suitable materials include, but are not limited toceramics (porcelain, alumina, hydroxyapatite, zirconia), polymers (e.g.thermoplastic elastomers (e.g. silicone elastomers, styrene blockcopolymers, thermoplastic copolyesters, thermoplastic polyesters,thermoplastic polyamides, thermoplastic polyolefins, thermoplasticpolyurethanes, thermoplastic vulcanizates), polyvinyl chloride,fluoropolymers (PTFE, modified PTFE, FEP, ETE, PFA, MFA), polyurethane,polycarbonate, silicone, acrylics, polypropylene, low densitypolyethylenes, nylon, sulfone resins, high density polyethylenes,natural polymers (cellulose, rubber, alginates, carrageenan), polyimide,polyether ether ketone), metals (e.g. gold, silver, titanium, platinum),metal alloys (e.g. stainless steel, cobalt alloys, titanium alloys),glass, and combinations thereof.

The leads 150, bonding pads 140 and electrical conductors 120 can bemade of a suitable conductive or semi-conductive material. The materialcan be flexible. The materials can be biocompatible. Suitable conductiveand semi-conductive materials include, without limitation, gold, silver,copper, aluminum, nickel, platinum, palladium, zinc, molybdenum,tungsten, graphite, Indium tin oxide, conductive organic polymers (e.g.polyacetylene, polyphenylene vinylene, polypyrrole, polythiophene,polyaniline, and polyphenylene sulfide), silicon, germanium, cadmium,indium, and combinations thereof.

In operation, a known electrical current can be passed through at leastone of the electrical conductors 120. A voltage is then induced in atleast one of the other electrical conductors 120 As such, inembodiments, where there are only two electrical conductors 120 (abipolar configuration) (see e.g. FIG. 1), a known current can be passedthrough one electrical conductor (120 a) and a voltage is then inducedin the other electrical conductor (120 b). As shown in FIG. 3, wherethere are more than two electrical conductors 120 a-d (e.g. a tetrapolarconfiguration), a current can be passed through the outer mostelectrical conductors 120 a,d and the induced voltage across the innerelectrical conductors 120 b,c can be measured. Other suitableconfigurations will be appreciated by those of skill in the art. In anyembodiment, the high-frequency and low frequency impedance can bemeasured from the induced voltages. As described elsewhere herein, thehigh-frequency and low-frequency impedance can be used to determine if aparticular region of tissue has been treated and/or the area and/orvolume of tissue that has been effectively treated.

Some tissues have anisotropic electrical properties, which can be due tothe directional growth of the cell. As such, in some instances it isdesirable to measure the electrical conductivities in two orthogonaldirections. With this in mind, attention is directed to FIG. 4, whichshows an embodiment of an electrical conductivity sensor configured tomeasure both high- and low-frequency impedance in two orthogonaldirections.

As shown in FIG. 4, the electrical conductivity sensor can have at leasttwo impedance sensors 110 and 111. The first impedance sensor 110 canhave a first set of electrical conductors 120 a-d. The second impedancesensor 111 can have a second set of electrical conductors 121 a-d. Thefirst 120 and second 121 sets of electrical conductors can be coupled toa substrate 160 and/or impedance sensor substrate 130 such that thefirst set of electrical conductors 120 and the second set of electricalconductors 121 are orthogonal to each other. In this way, the first 110and the second 111 impedance sensors can be said to be orthogonal toeach other in these embodiments.

While FIG. 4 shows the impedance sensors 110, 111 in a tetrapolarconfiguration it will be appreciated by those of skill in the art thatthey can be configured in any suitable manner, for example, aspreviously described with respect to FIGS. 1-3. Likewise, each impedancesensor 110, 111 can have at least two electrical conductors 120, 121. Insome embodiments, each impedance sensor 110,111 can have 3, 4, 5, 6, 7,8, 9, 10 or more electrical conductors. The impedance sensors 110, 111can have the same number or a different number of electrical conductors120, 121 as each other. The dimensions of these embodiments of theelectrical conductivity sensor 100 can be as described with respect toFIGS. 1-3 above. The electrical conductivity sensor 100 and componentsthereof can be made from suitable materials as previously described withrespect to FIGS. 1-3. As previously described, each electrical conductor120, 121, can be coupled to a bonding pad 140 a-d and 141 a-d via anelectrical leads 150 a-d and 151 a-d. The operation of each set ofelectrodes 120, 121 to measure impedance can be as described withrespect to FIGS. 1-3 above.

FIGS. 1-4 demonstrate embodiments of an electrical conductivity sensor100 that contain electrical conductors at a single location on theelectrical conductivity sensor 100. As described elsewhere herein it canbe desirable to measure the size of a treatment area in a tissue duringfocal ablation/cell membrane disruption therapy. During therapy, thelesion formed will grow in size, and as such, it can be desirable tomeasure this growth without the need for repositioning the electricalconductivity sensor, or probe that it can be coupled to, duringtreatment.

With this in mind, attention is directed to FIGS. 5-8 which showembodiments of an electrical conductivity sensor 100 that has a sensorarray. The electrical conductivity sensor 100 having a sensor array canbe configured to measure impedance. In some embodiments, the electricalconductivity sensor 100 having a sensor array 200 can be configured todetect both high- and low-frequency impedance having an impedance sensorarray 200. In some embodiments the sensor array 200 can be configured todetect another tissue characteristic, including but not limited to, pH,temperature, drug concentration, chemical concentration, gasconcentration and combinations thereof. As such, in some embodiments,the lesion/treated area front can be determined by measuring thesecharacteristics.

Discussion continues with FIG. 5 which shows one embodiment of anelectrical conductivity sensor 100 having an impedance sensor array 200.In the embodiments depicted by FIG. 5, the impedance sensor array 200has at least two impedance sensors 110 a-h. While FIG. 5 shows animpedance sensor array 200 having eight (8) impedance sensors 110, itwill be appreciated that the impedance sensor array 200 can have 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 14, 16, 17, 18, 19, 20 or moreimpedance sensors 110. Each impedance sensor 110 can be coupled to abonding pad 140 a-h and a common ground 210 via electrical leads 150 a-hand 152 a-h. While FIG. 5 shows an impedance sensor array 200 havingeight (8) bonding pads 140, it will be appreciated that the impedancesensor array 200 can have 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,14, 16, 17, 18, 19, 20 or more bonding pads 140. The dimensions of theseembodiments of the electrical conductivity sensor 100 can be asdescribed with respect to FIGS. 1-3 above. The electrical conductivitysensor 100 and components thereof can be made from suitable materials aspreviously described with respect to FIGS. 1-3. In some embodiments, theelectrical conductivity sensor 100 having an impedance sensor array 200can contain include two current injection electrodes on either end ofthe electrode array.

Measurement of low-frequency and/or high-frequency impedance of eachimpedance sensor 110 of the impedance sensor array 200 can be aspreviously described with respect to FIGS. 1-3. Further, differences inimpedance measurements between two or more different impedance sensors110 of the impedance sensor array 200 can be determined. In this way itis possible to determine the extent of the lesion formed by focalablation/cell membrane disruption therapy. Stated differently, thechange in the electrical impedance of different combinations ofimpedance sensors 110 of the impedance sensor array 200 can be evaluatedand the lesion size, and/or lesion/treated area front can be determinedbased on the impedance or other tissue characteristic measurementsevaluated. This is discussed in greater detail elsewhere herein.

In some embodiments, the sensors 110 can be functionalized with one ormore receptor molecules configured to specifically bind a targetmolecule. This can make the impedance measurement more selective towardidentification of certain intracellular substances, including proteinsand ions that are released during electroporation. This modification canenhance the capability of the sensor to detect the lesion front.

FIG. 6 shows another embodiment of an electrical conductivity sensor 100having an impedance sensor array 200. The impedance sensor array 200 hasat least two impedance sensors 110 a-e. While FIG. 6 shows an impedancesensor array 200 having five (5) impedance sensors 110, it will beappreciated that the impedance sensor array 200 can have 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 14, 16, 17, 18, 19, 20 or more impedancesensors 110. Each impedance sensor 110 can be coupled to a bonding pad140 a-e via electrical leads 150 a-e. While FIG. 6 shows an impedancesensor array 200 having five (5) bonding pads 140, it will beappreciated that the impedance sensor array 200 can have 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 14, 16, 17, 18, 19, 20 or more bonding pads140. The electrical impedance measured by any combination of impedancesensors can be determined and correlated to the lesion size. Thedimensions of these embodiments of the electrical conductivity sensor100 can be as described with respect to FIGS. 1-3 above. The electricalconductivity sensor 100 and components thereof can be made from suitablematerials as previously described with respect to FIGS. 1-3.

FIG. 7 shows further embodiments of an electrical conductivity sensor100 having an impedance sensor array 200. These embodiments are the sameas those described in relation to FIG. 6 except that they furthercontain a common counter electrode 220. The common counter electrode 220can be coupled to the substrate 160. The common counter electrode 220can be coupled to a bonding pad 230 via an electrical lead 240, whichboth can also be coupled to the substrate 160. In operation, allimpedances measured by the impedance sensors 110 of the impedance sensorarray 220 can be measured with respect to the common counter electrode220. It will be appreciated that a common counter electrode can also beused in embodiments described in FIG. 5. The dimensions of theseembodiments of the electrical conductivity sensor 100 can be asdescribed with respect to FIGS. 1-3 above. The electrical conductivitysensor 100 and components thereof can be made from suitable materials aspreviously described with respect to FIGS. 1-3.

FIG. 8 shows further embodiments of an electrical conductivity sensor100 having an impedance sensor array 200. The impedance sensor array 200can contain impedance sensors 110 having interdigitated electrodes 300.In embodiments, the impedance sensor can have a pair of electrode sets310 a,b (collectively 310), where each electrode set has an even numberof electrodes (e.g. 2, 4, 6, 8, 10 etc.) and can be interdigitated witheach other as shown in FIG. 8. This interdigitated configuration canincrease the sensitivity of the impedance sensor 110. While not beingbound to theory, it is believed that the increase in sensitivity can beattributed to the increased current density across the interdigitatedpair of electrode sets 310 relative to a non-interdigitated electrodeset.

While FIG. 8 shows an impedance sensor array 200 having five (5)impedance sensors 110, it will be appreciated that the impedance sensorarray 200 can have 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 14, 16,17, 18, 19, 20 or more impedance sensors 110. The impedance sensors 110can be coupled to a substrate 160 as previously described in relation toe.g. FIGS. 5-7. Each impedance sensor 110 can be coupled to a bondingpad 140 via electrical leads 150 a-e. While FIG. 8 shows an impedancesensor array 200 having five (5) bonding pads 140, it will beappreciated that the impedance sensor array 200 can have 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 14, 16, 17, 18, 19, 20 or more bonding pads140. In some embodiments, the impedance sensors can all be coupled to acommon ground 210 as previously described with respect to FIG. 5. Infurther embodiments, the electrical conductivity sensor 100 having animpedance sensors 110 with interdigitated electrodes 300 can furthercontain a common counter electrode 230, which can be configured as shownand described with respect to FIG. 7 The dimensions of these embodimentsof the electrical conductivity sensor 100 can be as described withrespect to FIGS. 1-3 above. The electrical conductivity sensor 100 andcomponents thereof can be made from suitable materials as previouslydescribed with respect to FIGS. 1-3.

In some embodiments, the electrical conductivity sensor 100 as describedin relation to any of FIGS. 1-8 can further contain one or moreadditional sensors to measure additional tissue characteristics.Additional sensors include, but are not limited to, pH sensors,temperature sensors, chemical sensors, and gas (e.g. CO₂, NO, O₂)sensors. There can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more additionalsensors. The additional sensors can also be configured as an array akinto the impedance sensor array on the electrical conductivity sensor 100.The additional sensor(s) can be coupled to the substrate 160. Theadditional sensors can be coupled to one or more additional bonding padsvia leads as will be appreciated by those of skill in the art.

The electrical conductivity sensor 100 and/or any component(s) thereofas described in relation to any of FIGS. 1-8 can be disposable,reusable, recyclable, biocompatible, sterile, and/or sterilizable.

The electrical conductivity sensor 100 and components thereof describedherein can be manufactured by any suitable method and in any suitableway. Suitable methods include, but are not limited to, injectionmolding, 3-D printing, glass/plastic molding processes, optical fiberproduction process, casting, chemical deposition, electrospinning,machining, die casting, evaporative-pattern casting, resin casting, sandcasting, shell molding, vacuum molding, thermoforming, laminating, dipmolding, embossing, drawing, stamping, electroforming, laser cutting,welding, soldering, sintering, bonding, composite material winding,direct metal laser sintering, fused deposition molding,photolithography, spinning, metal evaporation, chemical etching andsterolithography. Other techniques will be appreciated by those of skillin the art.

Electrical Conductivity Probes

The electrical conductivity sensors 100 described in relation to FIGS.1-8 can be coupled to or integrated with a probe. In some embodiments,the probe can be a treatment probe (i.e. the probe delivering the focalablation/cell membrane disruption therapy). The probe that contains theelectrical conductivity sensor 100 can be separate from the treatmentprobe. With the general concept in mind, attention is directed to FIGS.9-11, which show various embodiments of probes including electricalconductivity sensors 100 as described in relation to FIGS. 1-8. As shownin FIGS. 9-11, which show embodiments of an electrical conductivityprobe 400 having one or more electrical conductivity sensor 100 a,b,c(collectively 100). The electrical conductivity sensor(s) 100 can be anyelectrical conductivity sensor described in relation to FIGS. 1-8.

The electrical conductivity probe 400 can have an elongated member 410having a distal portion 420 and a proximal portion 430. The elongatedmember 400 can be any three dimensional shape, including but not limitedto, an irregular shape, a cylinder, a cannula, a cuboid, and atriangular prism. The elongated member 400 can have a width. The widthcan range from about 0.1 mm to about 10 mm or more. The elongated membercan have a length. The length can range from about 5 mm to about 50 cmor more. The elongated member can have a diameter. The diameter canrange from about 10 microns to about 10 mm or more. The distal portioncan have a tapered, beveled, pointed, blunt, sharp, rounded, or flatend. Other configurations for the elongated member will be appreciatedby those of skill in the ar. At least one electrical conductivity sensor100 a,b,c (collectively 100) coupled to or otherwise integrated with anouter surface of the elongated member. In some embodiments, 1, 2, 3, 4,5, 6, 7, 8, 9, 10 or more electrical conductivity sensors 100 can becoupled to the elongated member 410. In some embodiments the electricalconductivity sensor(s) 100 can be removably coupled to the elongatedmember 410. The electrical conductivity sensor(s) 100 can beelectrically coupled to the elongated member 410. The electricalconductivity sensor(s) 100 can be coupled to the elongated member in anydesired configuration, e.g. linearly, radially, and the like, as will beappreciated by those of skill in the art.

The electrical conductivity probe 400 can include sensors configured todetect tissue characteristics (e.g. pH, temperature, chemical, gassensors) and circuitry as needed. In some embodiments, the electricalconductivity probe 400 can be configured to deliver an energy to resultin focal ablation/cell membrane disruption in a tissue. Stateddifferently, the electrical conductivity probe 400 can also be atreatment probe in some embodiments. In other embodiments, theelectrical conductivity probe 400 can be separate from a treatmentprobe. The electrical conductivity probe 400 and/or components thereofcan be disposable, reusable, recyclable, biocompatible, sterile, and/orsterilizable.

In some embodiments, the impedance sensors and impedance sensor arrayscan be integrated directly with an elongated member 510 of an electricalconductivity probe 500. In other words, the impedance sensor andimpedance sensor arrays and associated circuitry are not coupled to asubstrate (e.g. 160, FIGS. 1-8), but rather directly integrated with anelongated member 510 of a probe. With this in mind attention is directedto FIGS. 12-13, which show embodiments of an electrical conductivityprobe 500 having one (FIG. 12) or more (FIG. 13) impedance sensors 110,which can be configured to measure tissue impedance, a change in tissueimpedance across regions of tissue, and/or both low-frequency (α region)impedance and high-frequency (β region) impedance. The impedancesensor(s) can be as described in relation to any of FIGS. 1-8. As shownin FIG. 13, the impedance sensor(s) can be positioned on the elongatedmember such that they can form an impedance sensor array 540. Theelongated member can be as described in relation to FIGS. 9-11.

The impedance sensor(s) 110 can be electrically coupled to the elongatedmember 410. The electrical conductivity probe 500 can include additionalsensors (e.g. pH, temperature, chemical, gas sensors) and additionalcircuitry as needed. In some embodiments, the electrical conductivityprobe 500 can be configured to deliver an energy to result in focalablation/cell membrane disruption in a tissue. Stated differently, theelectrical conductivity probe 500 can also be a treatment probe in someembodiments. In other embodiments, the electrical conductivity probe 500can be separate from a treatment probe. The electrical conductivityprobe 500 and/or components thereof can be disposable, reusable,recyclable, biocompatible, sterile, and/or sterilizable.

The electrical conductivity probes 400,500 described herein can bemanufactured by any suitable method and in any suitable way. Suitablemethods include, but are not limited to, injection molding, 3-Dprinting, glass/plastic molding processes, optical fiber productionprocess, casting, chemical deposition, electrospinning, machining, diecasting, evaporative-pattern casting, resin casting, sand casting, shellmolding, vacuum molding, thermoforming, laminating, dip molding,embossing, drawing, stamping, electroforming, laser cutting, welding,soldering, sintering, bonding, composite material winding, direct metallaser sintering, fused deposition molding, photolithography, spinning,metal evaporation, chemical etching and sterolithography. Othertechniques will be appreciated by those of skill in the art.

Real-Time Lesion/Treated Area Monitoring Systems

Also provided herein are lesion and treated area monitoring systems thatcan include one or more electrical conductivity probes and componentsthereof described in relation to FIGS. 1-13 that can monitor lesionformation during focal ablation/cell membrane disruption therapy.Discussion of the various systems begins with FIG. 13, which showsembodiments of a real-time lesion monitoring system 600. An electricalconductivity probe 610 can be coupled to an impedance analyzer 620. Theelectrical conductivity probe 610 can be any electrical conductivityprobe as described in relation to FIGS. 9-13. The impedance analyzer 620can be electrically coupled to the impedance sensor(s) 110 of theelectrical conductivity probe 610. In some embodiments, the impedanceanalyzer can contain one or more switches 630, where each switch can becoupled to a single impedance sensor on the electrical conductivityprobe 610.

The impedance analyzer 620 can include or be coupled to one or morecurrent injection electrodes 640 configured to inject a low voltage(0.1-1000 mV or more) signal into the impedance sensor(s) 110 of theelectrical conductivity probe 610. The injection electrode(s) 640 caneach be coupled to an impedance sensor 110 via a switch. Not all of theimpedance sensors need be coupled to an injection electrode 640. Stateddifferently, in some embodiments, only some of the impedance sensors arecoupled to an injection electrode via a switch. In some embodiments, theinjection electrodes 641 a,b are separate from the impedance sensor(s)110 and can be placed on the outside of an impedance sensor array 200.(see e.g. FIG. 13). The impedance analyzer and/or injection electrodescan be coupled to a low voltage power supply 650.

The impedance analyzer 620 can be coupled to and/or in communicationwith a computer or other data storage/processing device 660. Theimpedance analyzer 620 can be wirelessly coupled to the computer 660.The impedance analyzer can be hard wired to the computer 660. Thecomputer 660 can contain processing logic configured to analyze datafrom the impedance analyzer 620 or other sensor information receivedfrom the electrical conductivity probe 610 and determine the size of thelesion or treated area 730 in the tissue 740. The computer 660 cancontain processing logic configured to generate or initiate a signal(visual, audible, digital or otherwise) to alert a user that the lesionor treated are has reached a threshold size. The computer 660 cancontain processing logic that can be configured to analyze data receivedfrom the impedance analyzer 620 and/or electrical conductivity probe 610can contain processing logic configured to analyze data from theimpedance analyzer 620 or other sensor information received from theelectrical conductivity probe 610 and generate an electrical tomographicimage of the treatment area. In some embodiments, the processing logiccan be configured to determine the ratio of low-frequency impedance tohigh frequency impedance at a given impedance sensor 110 from impedancesensor data received from the impedance analyzer 620 and/or electricalconductivity probe 610. The computer 660 can contain processing logicconfigured to determine the amount of high voltage that should beapplied to the treatment area via a treatment probe 670 in response tothe impedance data and/or other sensory information received.

The computer 660 can be coupled to a waveform generator 680. Thewaveform generator 680 can be coupled to a gate driver 690. The gatedriver 690 and/or impedance analyzer 620 can be coupled to a highvoltage switch 700. The high voltage switch can be coupled to an energystorage device 710. The energy storage device can be coupled to a highvoltage power supply 720, configured to deliver a high voltage that canrange from 50 to 10000 V or more. A treatment probe 670 can be coupledto the high voltage switch 700. The high voltage switch 700 can becontrolled by and/or responsive to the waveform generator 680 and/orgate driver 690. Insofar as the waveform generator 680 and/or gatedriver 690 can be controlled by the computer 660, treatment can be, insome embodiments, autonomously controlled in response to impedance andother sensory data obtained by the electrical conductivity probe 610during treatment. The operation of the system is discussed in furtherdetail below.

In some embodiments, such as those shown in FIG. 15, the electricalconductivity sensor only includes one sensing area as opposed to anarray of sensors which provides ease of fabrication and could be used totell if the lesion front has reached a certain point rather thanmonitoring its location. The system 800 can be configured the same asthat described in relation to FIG. 13, except that a single probe 750,which can contains one or more impedance sensor or an impedance sensorarray, is coupled to both the high voltage switch 700 and the lowvoltage power supply 650.

Real-Time Lesion Front/Treated Area Monitoring

The devices and systems described herein can be used to monitor thelesion formation/front and/or treated area during focal ablation/cellmembrane disruption therapies, which include, but are not limited toradiofrequency (RF) ablation, microwave ablation, laser ablation,cryo-ablation, ultrasound, electroporation (reversible andirreversible), supraporation, and radiation therapy. Thus, these devicesand systems have application for tumor and undesired ablation, drugdelivery, and gene therapy and nucleic acid and other molecule delivery.In principle, an electrical conductivity probe as described in relationto FIGS. 1-13 can be inserted into a tissue. During focal ablation orcell membrane disruption, the treated portion of the tissue undergoeschanges due to changes in the permeability of the cell membrane. Thisresults in the formation of a lesion or treated area (e.g. area oftissue to which a drug or other molecule has been delivered). Astreatment continues the size of the lesion or treated area can grow.Impedance and other sensors on the electrical conductivity probe canmeasure electrical conductivity, pH, temperature, chemicals, and/orgasses at locations in the tissue. The systems and devices describedherein can then determine the lesion size based upon the electricalconductivity data and other sensory information determined by the probe.In some embodiments, the system can be configured to autonomouslycontrol the treatment probe such that when the lesion has reach adesired size, the system can stop treatment in the tissue. Inembodiments, the system can be configured to alert a user that thelesion/treated are has reached a desired size. In some embodiments, auser can alter treatment in response to the determined lesion/treatedarea size. The operation of the systems and devices is discussed ingreater detail with respect to FIGS. 16A-17C.

Discussion of the operation of the systems and devices begins with FIGS.16A-16B, which show monitoring of a lesion/treated area formation andfront using an electrical conductivity probe having an impedance sensorduring treatment (FIG. 16A) and at the treatment endpoint (FIG. 16B).The treatment probe is not shown in FIGS. 16A and 16B for clarity.However, it will be appreciated that treatment may be provided by aseparate treatment probe or be provided by the electrical conductivityprobe, which can be configured to deliver high voltage treatment as wellas measure tissue characteristics. FIGS. 16A-16B demonstrate monitoringof lesion/treated area formation and front during treatment when using asingle impedance sensor (or other sensor) or multiple impedance sensors(or other sensors) placed radially about the surface of the probe suchthat the sensors are all at the same point along the length of theprobe.

As shown in FIG. 16A, the electrical conductivity probe 900 can beinserted into the tissue 910. The electrical conductivity probe 900 canbe inserted into the tissue such that the impedance or other sensor isat the outer edge of the desired treatment area. As treatment begins, alesion or treated area 920 begins to form as the permeability of thecell membranes change. During this time impedance and/or other tissuecharacteristics are being measured by the sensor(s) 930 on theelectrical conductivity probe. The sensors (impedance or other types)can be as described in relation to FIGS. 1-8. As such, during treatment,the impedance and/or other tissue characteristics can be continuallydetermined during treatment and compared to prior measurements,including any baseline measurements taken prior to the start oftreatment, to determine if the lesion/treated area has reached thedesired size. As shown in FIG. 16B, when the lesion/treated area hasgrown such that it reaches the point in the tissue where the impedanceor other sensor(s) 930 is located, the sensor(s) will measure a changein electrical conductivity and/or pH, chemical concentration, gasconcentration, or other molecule concentration and the system can alerta user that the size of the lesion/treated area has reached the desiredsize. For example, in some embodiments, when the lesion/treated areareaches the sensor(s) 930 on the electrical conductivity probe 900, thelow-frequency impedance is equal to the high-frequency impedance. Inother embodiments, the system can automatically stop treatment via thetreatment probe in response to a detected change in the impedance orother tissue characteristic.

While systems and devices employing sensor(s) at a single point alongthe length of the probe can be suitable for some applications, they canonly determine the size of a lesion/treated area when it reaches asingle point. With that in mind attention is directed to FIGS. 17A-17C,which show the operation of an electrical conductivity probe having asensor array (e.g. an electrical impedance sensor array) duringtreatment. The treatment probe is not shown in FIGS. 17A-17B forclarity. However, it will be appreciated that treatment may be providedby a separate treatment probe or be provided by the electricalconductivity probe, which can be configured to deliver high voltagetreatment as well as measure tissue characteristics.

As shown in FIG. 17A, the electrical conductivity probe 900 can beinserted in a tissue 910 to be treated. Baseline impedance and othertissue characteristic measurements can be obtained prior to the start oftreatment. As treatment begins a lesion/treated area 920 can form in thetissue 910. During treatment the sensors of the sensor array 940 can bemeasuring impedance and/or other tissue characteristics (e.g. pH,chemical concentration, gas concentration, temperature, other moleculeconcentration, and the system (not shown for clarity) can be determiningif there is a change in the impedance and/or other tissuecharacteristics at any given sensor along the sensor array 940 orbetween any combination of sensors along the sensor array 940. As thelesion front/treatment area 920 grows (see FIG. 17B), the system willdetermine that there is a change relative to base line and/or that ofanother sensor in the impedance and/or other tissue characteristicbetween certain sensors within the array. From that data the system candetermine the size of the lesion and/or determine the position of thelesion front as the lesion grows during treatment. For example, as shownin FIG. 17B the lesion/treated area 920 has grown such that the lesionfront is between the second 950 b and third sensor 950 c of the sensorarray 940. As such, the system can determine that there is a change inthe impedance (or other tissue characteristic) at the second sensor 950b relative to baseline. The system can determine that there is no changein the impedance (or other tissue characteristic) at the third sensor950 c relative to baseline. From this, the system can determine that thelesion front/treated area has reached the position on the probe thatlies between the second 950 b and third 950 c sensor on the electricalconductivity probe 900. The process of continually measuring impedance(other tissue characteristic) by the sensors of the sensor array 940 andcomparing them to baseline/and or other data from other sensors of thesensor array 940 can continue until the lesion/treated area 920 hasreached a desired size. The desired size can be predetermined and thesystem can be configured to alert a user via a signal when the systemcalculates that the desired size has been reached. In other embodiments,the system can be configured to automatically stop treatment when thesystem calculates that the desired size has been reached.

It will be appreciated that any number of electrical conductivity probes900 can be used at the same time. By placing electrical conductivityprobes 900 at different locations and depths into the tissue, the dataprovided can be used by the system to determine a volume of thelesion/treated area and/or generate a three dimensional image of thetreated area.

EXAMPLES

Now having described the embodiments of the present disclosure, ingeneral, the following Examples describe some additional embodiments ofthe present disclosure. While embodiments of the present disclosure aredescribed in connection with the following examples and thecorresponding text and figures, there is no intent to limit embodimentsof the present disclosure to this description. On the contrary, theintent is to cover all alternatives, modifications, and equivalentsincluded within the spirit and scope of embodiments of the presentdisclosure.

Example 1

FIGS. 18-20 show images demonstrating an electrical conductivity sensoras described in relation to any of FIGS. 1-8. The fabricated probe isabout 15 micron thick, 8 cm long and 8 mm wide. The gold wires aresandwiched between two polyimide layers. The polyimide layer over thebonding pads and the sensor area is removed to expose these parts. Thesmall dimensions of the sensor can enable conductivity measurement witha high spatial resolution. The electrical conductivity sensor can bewrapped around a probe, such as an irreversible electroporation probe(IRE) or other treatment probe to create a device capable of bothtreating tissue with electroporation and monitoring the extent of thetreatment in real-time. In this probe, the conductivity measurement canbe conducted at one point next to the beginning of the exposed area ofthe IRE probe. The electrode can be flexible enough to be easily wrappedaround IRE probes with a small diameter of 1 mm. FIG. 21 shows an imageof an electrical conductivity sensor that has been coupled to an IREprobe.

Example 2

FIGS. 22A-22J demonstrate a fabrication process for the construction ofthe electrical conductivity sensor of Example 1. A 4″ Si wafer 2200 wasused as the fabrication substrate. The wafer edge was treated with asolution of adhesion promoter (HD Microsystems, Parlin, N.J.) to provideadhesion between the wafer 2200 and the polyimide layer 2210 (FIG. 22B).The adhesion should be enough to keep the construct on the wafer 2200during the fabrication steps. (FIG. 22B) Polyimide (HD Microsystems,Parlin, N.J.) substrate 2210 was spun and cured over the Si wafer 2200.The spin speed was adjusted to achieve a thickness of about 15 microns.The spin step could be repeated if a greater film thickness is desired.(FIG. 22C) A layer of about 300 nm of gold was deposited on thepolyimide layer by PVD. For a better adhesion of gold to the polyimidesubstrate a Cr layer 2200 was deposited first. (FIG. 22C) A photoresistlayer 2230 was spun and patterned as the desired gold electrodes usingthe photolithography techniques. FIG. 22D The patterned photoresist wasused as a mask for wet etching of gold in the next step. Gold and Crlayers were etched 2240 (FIG. 22E) using appropriate wet etchingsolutions and the photoresist layer 2230 was washed away. Another layerof polyimide 2250 was spun and cured to act as an insulator over theelectrode FIG. 22F. The insulator should cover the wires of theelectrode and leave the sensor and bond pads exposed. A Ti mask 2260 wasdeposited by PVD and patterned by photolithography techniques followedby wet etching (FIG. 22G). The Ti mask was used to etch the upperpolyimide layer in RIE (Reactive Ion Etching) to expose 2270 the sensingareas and bond pads (FIG. 22H). The Ti mask was washed away using wetetching (FIG. 22I). The whole electrode structure was peeled off the Siwafer 2200 (FIG. 22J). To protect the impedance electrodes from highvoltage electric discharge of the pulsing leads, a thin passivationlayer such as silicon dioxide or silicon nitride can be coated on thesensor area. This passivation layer acts as a capacitor which protectsthe sensor from high voltage of the DC pulses however has a minimalimpact on the AC impedance readings. Functionalization of the sensorswith receptor molecules configured to specifically bind a targetmolecule can performed after metal patterning as an option usingtechniques known in the art.

Example 3

A three dimensional finite element model was constructed in Comsol 4.2a(Burlington, Mass.) to simulate IRE treatment of liver tissue with twoneedle electrodes (FIGS. 23A-23B). The electric potential distributionwithin the tissue was obtained by transiently solving:

0=−∇·(α(|E|)∇Φ)  (Equation 1)

Where ϕ is the electric potential, E is the electric field, and a is theelectric conductivity. Equation 1 is obtained from Maxwell's equationsassuming no external current density (J=σE), no remnant displacement(D=ε₀ε_(r),E), and the quasi-static approximation. This approximationimplies a negligible coupling between the electric and magnetic fields(∇×E=0), which allows for the expression of electric field only in termsof electric potential:

E=−∇ϕ  (Equation 2)

As depicted in Equation 1, the electric conductivity is a function ofthe electric field magnitude. This equation is used to describe thenonlinear of effects of pore formation in the cell membrane at thetissue scale. Specifically, this can be described by a step functionwith a certain degree of smoothing, or by other functions that followsimilar relationships between the electric conductivity and electricfield, such as sigmoid or Gompertz functions. The step function chosenhere increased from a baseline conductivity of 0.3 S/m to a plateau of1.05 S/m across a transition zone of 500 V/cm centered at 500 V/cm.Therefore, regions of tissue subject to an electric field above 750 V/cmwere maximally electroporated.

An electric potential boundary condition of 1500 V was applied along theenergized surface of one of the electrodes, with the correspondingground portion of the alternate electrode set to 0 V. The dielectricproperties of the exposed portion of the electrodes for performing IREand the insulative portion for protecting healthy tissue can be found inGarcia, P. A., et al., Intracranial Nonthermal IrreversibleElectroporation: In Vivo Analysis. Journal of Membrane Biology, 2010.236(1): 127-136. All remaining interior boundaries were treated ascontinuity, and all remaining outer boundary conditions were treated aselectrical insulation. The stationary problem consisting of 100,497 meshelements was solved using an iterative, conjugate gradient solver.

The electrical conductivity in the tissue resulting from IRE is shown inFIG. 24A. Experimentally, voltage drop measurements made between anycombination of sensing electrodes can be used to determine thisconductivity. Through comparisons to electrical measurements made priorto treatment, it is then possible to determine the extent to whichtissue adjacent to each of the sensors has undergone electroporation. Ifimpedance measurements are obtained between electroporative pulses of amultiple pulse protocol, then a real-time, dynamic representation of howthe treated tissue expands along the length of the electrode can beobtained. Point specific measurements can also be extrapolated in threedimensions to determine the spatial-temporal conductivity map andelectric field distribution (FIG. 24B).

Example 4

FIGS. 25A-27 describe results of delivering a series of high-frequencyirreversible electroporation (HFIRE) pulses to porcine liver through thehigh voltage portion of a probe that also contains an impedance sensorarray. FIG. 25A shows an experimental probe model with 5 microelectrodesand 4 sensing pairs (SP). In FIG. 25B, TTC Stained HFIRE ablation inliver (2000 V) can be observed in which viable tissue was stained redwhile dead tissue whitened. Ablation (marked by dotted line) reachedonly SP1. The impedance signature throughout delivery of HFIRE pulses asmeasured by SP1 is shown in FIG. 26). The largest change in impedancewas observed at 5 khz, which indicated current was no longer confined toextracellular pathways and its flowing through the cellmembrane—indicating electroporation of tissue. This progressive declinein resistance can be used to monitor ablation growth throughout thetherapy. FIG. 27 presents the resulting changes in tissue impedanceduring HFIRE therapy at 5 khz. Major changes in impedance were onlyobserved on probe pair in contact with treated tissue (FIG. 25B). FEMresults for electric field distribution along the length of the probefor different pulse parameters can be correlated to thesespatio-temporal changes in electrical conductivity during IRE proceduresto indicate the electric field threshold for cell death in a tissue ofinterest.

Example 5

A real-time visualization tool for monitoring of reversible andirreversible electroporation treatments. Once the threshold for celldeath in terms of bulk tissue conductivity has been characterized thisinformation can be used to reconstruct the ablation in 3D. The volume ofthe ablation geometry can be described in 2D with a Cassini oval plotthat has the results from one axis extrapolated into a third dimension.

The Cassini oval is a curve that derives its values based on thedistance of any given point, a, from the fixed location of two foci, q₁and q₂, located at (x₁, y₁) and (x₂, y₂). The equation is similar tothat of an ellipse, except that it is based on the product of distancesfrom the foci, rather than the sum. This makes the equation for such anoval:

[(x ₂ −a)²+(y ₂ −a)²]=b ⁴  (Equation 3)

where b⁴ is a scaling factor to determine the value at any given point.For incorporation of this equation into shapes that represent theelectric field distribution, it is assumed that the two foci are locatedat the center of the pulsing electrodes along the length of the probe(e.g., x-axis) at (±x,0).

Here, the parameter a represents the location of the ablation frontalong the length of an IRE needle. This is used to solve for b giving acomplete equation to describe the ablation volume. After the probe isplaced, software can record baseline values for impedance along amicro-sensor array. After treatment begins, impedance measurements canbe recorded in real-time. The location of the ablation(lesion) front canbe determined according to the characteristic conductivity of the tissueof interested after it has been irreversibly electroporated. Finally,this data can be used to calculate the ablation geometry, which can beprojected as a 3D isometric view of SMART probe onto ortho-planes fromstacked CT images of patient anatomy (FIG. 28A). Similarly, the ablationprogression can be observed during treatment at 10 (green), 50 (red),and 100 (blue) pulses in axial (FIG. 28B), sagittal (FIG. 28C), andcoronal planes (FIG. 28D). Ultimately this system can provide healthcareprofessions and other practitioners with real-time feedback of any IREtherapy, by displaying the ablation volume relative to a targeted tumorin medical scans such as MRI, PET, or CT.

Example 6

FIGS. 29A-31C describe parts of the methodology related to determiningthe location of the ablation front and the resulting geometry of thevolume of ablation from a series of irreversible electroporation (IRE)pulses through the high voltage portion of a bipolar probe, alsocontaining an impedance sensor array. FIGS. 29A-29C shows the finiteelement model (FEM) results for electric field distribution along thelength of the probe for IRE pulses with a magnitude of 1500V. The dottedline corresponds to a characterized threshold for cell death dependentof a specific number of pulses (N) (e.g., 10, 30, 100). After the tissuehas been treated with several IRE pulses an ablation front can bedetected in the form of a change in tissue resistivity at differentpoints along the probe (FIGS. 30A-30C). FIGS. 31A-31C shows theresulting volumes of ablation post IRE treatments 10, 30 and 100 pulsesof 1500V.

Lesion growth in the perpendicular direction of the probe is alsoreflected in the impedance measurement by the probe. For example, it ispredicted by FEM model (FIGS. 29A-29C, solid line) and observed in FIGS.31A-31C that for 30 and 100 pulse treatments, probes 1 and 2 would fallwithin the lesion. However, the corresponding impedance measurementshows 400% and 500% increase in conductivity for 30 and 100 pulses,respectively. This difference is attributed to the depth of lesion inthe perpendicular direction. For the case of 10 pulses of 1500V, thesmall depth of the lesion in perpendicular direction and the marginallocation of probe 2 compared with the lesion, results in 200% relativeconductivity for sensors 1-2 measurement. For all treatments, themeasurements showing 100% relative conductivity correspond to electrodescompletely outside of the lesion.

These experimental results show that device (electroporation leads andmicro-electrode array) used during these experiments is not only capableof monitoring the lesion length along the probe, but also gives relevantinformation regarding its other dimensions. This information whencombined with FEM modeling can give accurate shape and size of thelesion.

Example 7

FIG. 32 shows a diagram demonstrating how the electrical connections toa conductivity probe 1000 can be made through conductive flexiblesilicon pads or any other flexible conductive material or structure thatcan be installed in the handle and in opposite side of the conductivepads 140. The conductive silicon pads can be connected to the externalwires. Upon assembly, the conductive silicon pads come in conformalcontact with the gold pads on the conductivity sensor and make theelectrical connection.

Example 8

FIG. 33A shows a graph demonstrating the impedance spectrum of porcineliver as measured by the conductivity sensor. Fitting of the spectrum tothe equivalent circuit model of tissue reveals critical tissueproperties at cellular level which could be used for determination oflesion size during ablation. FIG. 33B shows one example of tissueelectric circuit model.

Example 9

FIGS. 34 and 35 demonstrate additional embodiments of a systemconfigured to monitor a lesion/treated area front in real-time. In thisembodiment, the high voltage energy for tissue ablation can be deliveredto the tissue through a single high voltage probe and a large groundingpad, which can be positioned on the surface of the organ/tissue. Due toelectric field concentration around the tip of the high voltageelectrode, a spherical lesion can form. The spherical lesion can bemonitored using the conductivity sensor as described before.

1. An electrical conductivity sensor comprising: an impedance sensor,where the impedance sensor is configured to measure a low-frequency anda high-frequency impedance; and a substrate, where the impedance sensoris coupled to the substrate.
 2. The electrical conductivity sensor ofclaim 1, wherein the substrate is flexible.
 3. The electricalconductivity sensor of claim 1, wherein the impedance sensor comprisestwo or more electrical conductors.
 4. The electrical conductivity sensorof claim 3, wherein the electrical conductors are in a bipolarconfiguration.
 5. The electrical conductivity sensor of claim 4, whereinthe electrical conductors are in a tetrapolar configuration.
 6. Theelectrical conductivity sensor of claim 3, wherein two impedance sensorsare coupled to the substrate such that they are orthogonal to eachother.
 7. The electrical conductivity sensor of claim 3, wherein theimpedance sensors are configured in an array.
 8. The electricalconductivity sensor of claim 7, further comprising a common ground,wherein each impedance sensor is coupled to the common ground.
 9. Theelectrical conductivity sensor of claim 7, further comprising a commoncounter electrode, wherein the common counter electrode is coupled tothe substrate.
 10. The electrical conductivity sensor of claim 1,wherein the impedance sensor comprises interdigitated electrodes. 11.The electrical conductivity sensor of claim 1, wherein the impedancesensor(s) further comprise a receptor molecule configured tospecifically bind a target molecule, wherein the receptor molecule iscoupled to the sensor(s).
 12. The electrical conductivity sensor ofclaim 11, wherein the impedance sensor comprises interdigitatedelectrodes.
 13. The electrical conductivity sensor of claim 11, furthercomprising one or more sensors configured to detect a tissuecharacteristic selected from the group of: pH, temperature, a chemicalconcentration, a nucleic acid concentration, a gas amount, orcombinations thereof.
 14. The electrical conductivity sensor of claim10, further comprising one or more sensors configured to detect a tissuecharacteristic selected from the group of: pH, temperature, a chemicalconcentration, a nucleic acid concentration, a gas amount, orcombinations thereof.
 15. The electrical conductivity sensor of claim 1,further comprising one or more sensors configured to detect a tissuecharacteristic selected from the group of: pH, temperature, a chemicalconcentration, a nucleic acid concentration, a gas amount, orcombinations thereof.
 16. An electrical conductivity probe comprising:an elongated member; and an electrical conductivity sensor as in claim1, wherein the electrical conductivity sensor is coupled to theelongated member.
 17. The electrical conductivity probe of claim 16,wherein the electrical conductivity sensor is removably coupled to theelongated member.
 18. A system comprising: an electrical conductivityprobe as in claim 17; a treatment probe configured to deliver an energyto a tissue, where the energy is sufficient to disrupt a cell membrane;an impedance analyzer, where the impedance analyzer is coupled to theelectrical conductivity probe; a low voltage power supply, where the lowvoltage power supply is coupled to the electrical conductivity probe andis configured to deliver a low voltage energy to the electricalconductivity probe; a waveform generator, where the waveform generatoris coupled to the low voltage power supply; a gate driver, where thegate driver is coupled to the waveform generator and the low voltagepower supply; a high voltage switch, where the high voltage switch iscoupled to the treatment probe and the impedance analyzer; and a highvoltage power supply, where the high voltage power supply is coupled tothe high voltage switch.
 19. The system of claim 18, further comprisinga computer, wherein the computer is coupled to the impedance analyzerand wherein the computer comprises processing logic configured todetermine the position of lesion or treated area front within a tissueundergoing focal ablation/cell membrane disruption therapy.
 20. Thesystem of claim 19, wherein the processing logic is further configuredto generate a signal to a user when the position of lesion or treatedarea front has reached a predetermined position within the tissue.21-35. (canceled)